There were upwards of a million total troops on the allied side, only about 200k made it on the actual D-Day. Nazi defenses were insane, under the command of Rommel, he has improvised thousands of miles of defensive lines throughout German occupied coastlines
Level 4 needs work, seriously. F***ing computer has a magical endless supply of money it doesn't have to blow on upgrades I have to save for two levels for... and they get a new restaraunt and the 7500 item... in 2 levels. They get something new and expensive every level. Where the f*** do they get the rest?
As for 13-- Concentrate units, try to anticipate where red will try and take one from you, and thirdly, always leave like 3 nanos at a cell, the more you cost the enemy to take the cell, the less you need to send to take it, meaning you have more to send to neutral cells.